The Wnt receptor Ryk is required for Wnt5a-mediated axon guidance on the contralateral side of the corpus callosum

Ryk (receptor related to tyrosine kinase) has been shown to be a novel Wnt receptor in both Caenorhabditis elegans and Drosophila melanogaster. Recently, Ryk-Wnt interactions were shown to guide corticospinal axons down the embryonic mouse spinal cord. Here we show that, in Ryk-deficient mice, cortical axons project aberrantly across the major forebrain commissure, the corpus callosum. Many mouse mutants have been described in which loss-of-function mutations result in the inability of callosal axons to cross the midline, thereby forming Probst bundles on the ipsilateral side. In contrast, loss of Ryk does not interfere with the ability of callosal axons to cross the midline but impedes their escape from the midline into the contralateral side. Therefore, Ryk(-/-) mice display a novel callosal guidance phenotype. We also show that Wnt5a acts as a chemorepulsive ligand for Ryk, driving callosal axons toward the contralateral hemisphere after crossing the midline. In addition, whereas callosal axons do cross the midline in Ryk(-/-) embryos, they are defasciculated on the ipsilateral side, indicating that Ryk also promotes fasciculation of axons before midline crossing. In summary, this study expands the emerging role for Wnts in axon guidance and identifies Ryk as a key guidance receptor in the establishment of the corpus callosum. Our analysis of Ryk function further advances our understanding of the molecular mechanisms underlying the formation of this important commissure

Strain engineering of germanium surface states: an ab-initio study.

Nanostructures have received growing interests in the last decade as consequence of their peculiar and fascinating properties, and applications often superior to their bulk counterparts. In the last few years surfaces and interfaces strongly influenced the electronic properties of semiconductor nanostructures. Nanomembranes (NMs) provide the opportunity for such quantitative investigations; they are two-dimensional crystalline films that can be shaped with precise surface orientations and sizes. My work connects with this widespread focus on two dimensional materials, with the aim of working out a novel understanding of the electronic band-gap engineering of the (2x1)-reconstructed Ge(001) surface, by means of ab-initio density functional theory numerical techniques. The truncation of the germanium crystalline structure along the [001] direction generates the (001)-oriented surface of germanium. At room temperature, this (ideal) surface is energetically unstable so that a process of atomic rearrangement occours which leads to (2x1) reconstructions, where (2x1) means that the surface periodicity is doubled along the [110] or the [$\bar1$10] crystallographic directions. In fact, on ideally-terminated (001) surfaces of the diamond lattice, each surface atom exhibits two dangling bonds, partly occupied. The process of formation of dimers on the Ge (001)-oriented surface is driven by halving the number of surface dangling bonds due to the establishment of a chemical bond between two neighbour Ge atoms on the surface. The angular orientation of the dimer has been longly debated, but eventually it was experimentally observed that it is tilted with respect to the surface plane; the asymmetry of the dimers plays a central role in the electronic properties of the (2x1) Ge (001) surface: the semiconductive character of the surface is the most important effect due to this asymmetry. The termination of a crystal with a surface and the successive rearrangment of surface atoms leads to a change of the electronic band structure with respect to the bulk material. In fact, electronic surface-localized states may exist at the semiconductor surface. In previous works the study of these surface states was confined to the unstrained (2x1) Ge (001) surface. Indeed, for low-dimensional as well as for three-dimensional crystalline materials a rich family of properties and functionalities can be tuned by strain-engineering, i.e., varying structural parameters, because their electronic and geometrical structures are sensitive to strain. In this work I study for the first time, by means of ab-initio techniques, the strain-engineering of the structural and electronic properties of the (2x1)-reconstructed Ge (001) surface. Such techniques have revealed to be invaluable tools to investigate crystalline structures (three or low-dimensional), interpret experimental measurements, give fundamental support in many solid state physics fields and design new devices, also due to the everlasting increase of computational capabilities. Nevertheless, these numerical techniques need to be handled and tuned carefully according to the working situations. For this reason, before focusing on the (2x1) Ge (001) surface electronic band-engineering, we found necessary to start from the study of the Ge bulk crystal, under relaxed or strained conditions, and of the unstrained (2x1) Ge (001) surface. These steps are necessary to rightly tune, by a fair comparison with known experimental results, the choices of the computational and working procedures to be finally used in the study of the strained (2x1) Ge (001) surface. The main conclusion of this work is the evidence that it is possible to manipulate the Ge(001) surface states relative to the bulk band structure. We demonstrate that by appropriate compressive strain it is possible to obtain pure surface states which can be exploited for surface transport experiments and optical transitions. The choice of germanium for the present investigation is that it is an ideal material to achieve integrated optical sources for silicon photonics, in particular on the (001) silicon surface which is at the heart of modern semiconductor devices

Correlazione fra gradiente alveolo-arterioso, rapporto P su F e reperti TC nelle polmoniti associate a COVID-19 nel Dipartimento di Emergenza-Urgenza

Background. Since one of the most common COVID-19 presentation in the Emergency Department is pneumonia with respiratory failure, it is essential an early stratification of its severity. Study design and methods. In this single center, observational, retrospective study we analyzed 112 patients with COVID-19 pneumonia, with focus on the relationship between P/F, A-a gradient and CT findings. Lung involvement has been evaluated with CT scan, as percentage (<25%, 26-50%, >50%) and type of parenchymal damage (ground glass opacity, infiltrates). Results. We found strong correlation between gas exchange impairment and outcome with significant P/F decreasing and A-a gradient increasing in dead subgroup (p < 0.0001). Association between A-a and CT data resulted significant (p < 0.05) from mild to severe pneumonia; association between P/F and CT resulted significant (p < 0.05) only for severe disease (> 50%). Patients with CT pattern of ground glass opacity and infiltrates had the worst prognosis, but interpretation of these results is difficult due to overlap of values between subgroups. Conclusions. Severity of respiratory failure at ED presentation is associated with type and percentage of parenchymal damage and has prognostic value. Due to the small population, further studies are needed to establish if lung damage and severity illness can be reliably predicted by blood gas analysis findings alone, reserving CT scan for specific cases such as of suspected pulmonary thromboembolism

Nutritional requirements and strain heterogeneity in Ashbya gossypii

Colony radial growth rates and specific growth rates of three related Ashbya gossypii strains ATCC10895, IMI31268, MUCL29450 and an unrelated strain, CBS109.26, were measured on various carbon and nitrogen sources at pH 4.5 and pH 6.5 to elucidate physiological growth requirements and strain differences. All strains grew on yeast extract or ammonium as nitrogen sources, but not on nitrate. Substantial growth at pH 4.5 was observed only on complex medium. D-Glucose, glycerol and starch were utilised as carbon sources. Ethanol was produced during growth on glycerol. Conversion of xylose into xylitol demonstrates that the xylose reductase is active. Phenotypic differences between related strains were greater than expected. We demonstrate that A. gossypii utilizes ammonium as sole nitrogen source at pH 6.5, facilitating further physiological studies using chemically defined media in the future.The financial support of Fundacao para a Ciencia e a Tecnologia (FCT), Portugal, is acknowledged, project AshByofactory PTDC/EBB-EBI/101985/2008 and grant SFRH/BD/30229/2006 to O. Ribeiro

The Role of State-Owned Enterprises in Promoting High-Quality Economic Development: The Case of China

The Chinese economy is attempting to undergo a critical transition, shifting from a growth model driven by the intensive exploitation of traditional production factors to one centered on high-quality economic development. This new stage prioritizes regional coordination, environmental sustainability, trade and investment openness, and income redistribution to enhance the economy’s potential for innovation. This study argues that specific features of China’s socialist system endow state-owned enterprises with the institutional capacity to effectively address structural barriers that could hinder this transition. The findings indicate that the growth of state-owned industrial capital significantly contributes to reducing regional disparities, promoting environmental sustainability, fostering international openness, and mitigating social inequalities. Furthermore, the combined growth of state-owned and private industrial capital has a long-term positive impact on innovation capacity. These results suggest that market socialism effectively allocates resources to support the development of productive forces in economies navigating the challenges of transitioning beyond middle-income status